Novel `synthetic metals' based on symmetrically tetrasubstituted nickel phthalocyanines

Nickel(II) 2,9,16,23-tetrasubstituted phthalocyanines, NiPTX (where X=–OH, –NO₂, –NH₂ and –SO₃H) were synthesized in pure state and doped with iodine. Elemental analysis, UV-Vis, infrared, X-ray diffraction, magnetic susceptibility and TGA studies were used to investigate the effects of iodine doping as well as substituents on the properties of the complexes. The electrical conductivity of nickel phthalocyanine derivatives found to depend on the nature of the substituents and showed ∼10³–10⁵ times increased electrical conductivity in comparison to parent nickel phthalocyanine. Further, the substitution and iodine doping show remarkably very high improved electrical conductivity nearly 10¹¹ times the electrical conductivity of nickel phthalocyanine.     

Synthesis, photophysical and photochemical properties of crown ether substituted zinc phthalocyanines

The photophysical and photochemical properties of the tetra- and octa-12-crown-4-substituted zinc (II) phthalocyanines are reported for the first time in the scope of this work. The new compounds have been characterized by elemental analysis, IR, ¹H and ¹³C NMR spectroscopy, electronic spectroscopy and mass spectra. General trends are described for photodegradation, singlet oxygen and fluorescence quantum yields, and fluorescence lifetimes of these compounds in dimethylsulphoxide (DMSO). Photophysical and photochemical properties of phthalocyanine complexes are very useful for photodynamic therapy (PDT) applications. The effects of the substituents on the photophysical and photochemical parameters of the zinc (II) phthalocyanines (5, 6 and 7) are also reported. The singlet oxygen quantum yields (Φ_Δ) ranged from 0.48 to 0.78 are indicating the potential of the complexes as photosensitizers in applications of PDT. The fluorescences of the substituted ZnPc complexes are effectively quenched by benzoquinone (BQ).     

Synthesis,photophysics, photochemistry and fluorescence quenching studies on highly soluble substituted oxo-titanium(IV) phthalocyanine complexes

The synthesis, photophysical and photochemical properties of soluble 3,4-(methylendioxy)-phenoxy substituted oxo-titanium(IV) phthalocyanines (4–6) are reported for the first time. The new compounds have been characterized by elemental analysis, FT-IR, ¹H NMR spectroscopy, electronic spectroscopy and mass spectra. General trends are described for fluorescence lifetimes and fluorescence, photodegradation and singlet oxygen quantum yields, of these compounds in dimethylsulfoxide (DMSO) and toluene. The effects of the position of the substituents and solvent effect on the photophysical and photochemical parameters of the oxo-titanium(IV) phthalocyanines (4–6) are also reported. The fluorescence of the substituted oxo-titanium(IV) phthalocyanine complexes (4–6) is effectively quenched by 1,4-benzoquinone (BQ) in both DMSO and toluene.     

Phthalocyanines in organized microheterogeneous systems. Review

Supramolecular organization of phthalocyanines (Pc) and the possible techniques of preventing Pc aggregation in an aqueous environment, including the use of surfactants, are analyzed. Peculiarities of the formation of supramolecular aggregates based on Pc and a number of biocompatible surfactants, as well as the prospects of using them in photodynamic therapy, are discussed. Attention is paid to crown-containing individual and metal phthalocyanines in organized microheterogeneous systems. Synergistic effects of non-covalent interactions, such as host-guest complex formation of Na⁺ ions and crown fragments, as well as electrostatic and hydrophobic interactions, provide the high selectivity of the formation of micelle-bound Pc monomers in the presence of a number of anionic surfactants, which enables one to consider crown-containing phthalocyanines as promising compounds in photodynamic therapy.     

Synthesis and electrochemical,in situ spectroelectrochemical,electrical and gas sensing properties of ball-type homo- and hetero-dinuclear phthalocyanines with four [1a,8b-dihydronaphtho[b]naphthofuro[3,2-d]furan-7,10-diyl] bridges

The new mono-nuclear Fe^II 2 and ball-type homo-dinuclear Fe^II–Fe^II 3 phthalocyanines have been synthesized from the corresponding 4,4′-(1a,8b-dihydronaphtho[b]naphthofuro[3,2-d]-furan-7,10-diyl)bis(oxy)diphthalonitrile 1 while ball-type hetero-dinuclear Fe^II–Co^II phthalocyanine 4 was synthesized from 2. The compounds have been characterized by elemental analysis, UV–vis, IR and MALDI-TOF-mass spectroscopies. The redox behaviours of the complexes were identified by controlled-potential coulometry, cyclic voltammetry and differential pulse voltammetry measurements on Pt in dimethylsulfoxide containing tetrabutylammonium perchlorate. The assignments of the redox processes and the understanding of the interactions between the metal phthalocyanine units in 3 and 4 were achieved by the combined evaluation of the voltammetric and in situ spectroelectrochemical outcomes. Complex 3 showed ring-based mixed-valence behaviour as a result of the considerable interaction between the phthalocyanine rings. On the other hand, the interactions between the two metal phthalocyanine units of 4 were found to be much weaker than those in 3. The potential application of molecular organic semiconductors needs the control adjustment of conductivity. Ac and dc conductivity measurements were performed with the applied external electric filed. At high frequency, the conduction follows the universal power law and conduction mechanism can be explained by classical hopping barriers mechanism for the system.     

Comparison of photophysicochemical properties of hexaphenoxycyclotriphosphazenyl-substituted metal-free,mono- and bis-lutetium phthalocyanines

The aim of this study is to compare the photophysicochemical properties of hexaphenoxycyclotriphosphazenyl-substituted metal-free (1), mono-(phthalocyaninato) lutetium(III) (2) [Lu^III(AcO)(Pc)] (Pc = phthalocyaninato, AcO = acetate) and bis-(phthalocyaninato) lutetium(III) (3) [Lu^IIIPc₂]. The synthesis and characterization (using the elemental analysis, mass spectrometry, IR, ¹H, and ³¹P NMR and UV–vis spectroscopy) of new compounds (2, 3) are described in this study. The electronic absorption and fluorescence spectral properties of compounds 1–3 are investigated. Photophysical (fluorescence quantum yields and lifetimes) and photochemical (singlet oxygen and photodegradation quantum yields) measurements are also studied on hexaphenoxycyclotriphosphazenyl-appended metal-free, mono- and bis-lutetium phthalocyanines in dimethylsulfoxide (DMSO). Photophysical and photochemical properties of phthalocyanines are very useful for photodynamic therapy (PDT) applications. Singlet oxygen quantum yields (Φ_Δ) give an indication of the potential of the complexes as photosensitizers in PDT applications. Hexaphenoxycyclotriphosphazenyl-substituted mono-(phthalocyaninato) lutetium(III) complex (2) gave good singlet oxygen quantum yield (0.66) in DMSO. Thus, this complex shows potential as Type II photosensitizer for PDT of cancer.     

Preparation,characterization, electrochemistry and in situ spectroelectrochemistry of novel α-tetra[7-oxo-3-(2-chloro-4-fluorophenyl)coumarin]-substituted metal-free,cobalt and zinc phthalocyanines

In this study, a novel ligand, 7-(2,3-dicyanophenoxy)-3-(2-chloro-4-fluorophenyl)coumarin was synthesized by the reaction of 3-(2-chloro-4-fluorophenyl)-7-hydroxycoumarin with 1,2-dicyano-3-nitrobenzen in dry DMF as the solvent in the presence of K₂CO₃ as the base. The preparation of the corresponding phthalocyanines H₂Pc, CoPc and ZnPc, substituted with 7-oxo-3-(2-chloro-4-fluorophenyl)coumarin functional groups at α positions of the Pc ring, was achieved by the cyclotetramerization of the coumarin ligand without any metal salts or with the relevant metal(II) acetates in 2-N,N-dimethylaminoethanol. The structures of the compounds were confirmed by elemental analysis, UV–vis, IR, MALDI-TOF mass and ¹H NMR spectra. In addition, aggregation and redox properties of the novel phthalocyanines with four halogenated coumarinoxy substituents at α positions of the phthalocyanine ring were compared with those of previously reported corresponding ones with β-substitution, by UV–vis spectroscopy, in situ spectroelectrochemistry and voltammetry. Remarkable differences in these properties between α- and β-substituted compounds were detected, and discussed in detail.     

Modification and application of metal phthalocyanines in heterogeneous systems

This review discusses the main aspects of synthesis, structural modification, and practical application of an extremely important class of organic heterocyclic compounds, phthalocyanines and their metal complexes. The main attention is paid to application of phthalocyanines, in such promising areas as tribologically active systems, functional composite materials and coatings, and supramolecular chemistry.     

Mass-balance and Eh-pH diagrams of Fe green rust in aqueous sulphated solution

The properties of a Fe^II-Fe^III mass-balance diagram are presented. Each compound is represented by a point P(x, R), where x=n_Fe^III/[n_Fe^II+n_Fe^III] is the ferric molar fraction and R=n_OH^-/[n_Fe^II+n_Fe^III] the number of mole of hydroxyl species necessary to precipitate one mole of iron in a given compound. If a chemical reaction leads to a given point P(x, R) in the diagram, the nature and relative abundance of the various iron species can be predicted by using simple rules that resemble those commonly used when studying binary and ternary phase diagrams. Reactions of oxidation of Fe^II species or coprecipitation reactions of Fe^II and Fe^III species are represented by different routes in the diagram. The evolution of the measured pH and redox potential E_h values during a controlled Fe^II oxidation experiment using sodium persulphate is explained by comparing the mass-balance and the E_h-pH Pourbaix diagrams. These values are also measured at the intersecting points of various routes and identical equilibrium conditions are often obtained. By displaying the involved chemical reactions, the Fe^II-Fe^III mass-balance diagram allows to understand the reaction path consequently followed in the E_h-pH Pourbaix diagram.     

Structural and magnetic properties of metal complexes constructed by pyridine-2,6-dicarboxylate and 5-(4-bromophenyl)-2,4′-bipyridine

Pyridine-2,6-dicarboxylic acid reacts as the first ligand (L1) under hydrothermal conditions with different metal ions such as Co^II, Ni^II, and Cu^II to form two 1D polymeric complexes [M(L1)(L2)₂·H₂O]_n (M = Co²⁺ or Ni²⁺) and a tetranuclear cluster with formula [Cu₄(L2)₄(L1)₄]·2H₂O in the presence of 5-(4-bromophenyl)-2,4′-bipyridine as the second ligand (L2). Intramolecular interactions were observed in the three compounds, being antiferromagnetic in both cobalt and nickel 1D coordination polymers and ferromagnetic interaction in the tetranuclear copper cluster.     

Synthesis,characterization and electrical and CO2 sensing properties of triazine containing three dendritic phthalocyanine

The metal-free phthalocyanine 1a was synthesised by statistically mixed condensation of 4-nitrophthalonitrile and 4-(2-dimethylaminoethylsulfanyl)phthalonitrile in dry 2-(dimethylamino)ethanol. The same route were applied to prepare metal-containing phthalocyanines using metal salts Zn(OAc)₃·2H₂O and CoCl₂, respectively, in dry DMF. The nitro compounds were reduced to amine with sodium sulfide and quarternized by reaction of MeI. These compounds were then reacted with cyanuric chloride in the presence of potassium carbonate as a base in mixture of THF and DMF gave s-triazine containing three amino phthalocyanines 4a–c. The reaction of three phthalocyanines with sodium salt of triethylmethanetricarboxylate in absolute ethanol were synthesised first generation of dendrimer 5a–c. The second generation of dendritic phthalocyanines 6a–c were prepared by the reaction of dentritic phthalocyanines with tris (H₂NC(CH₂OH)₃) using K₂CO₃ as a base in DMSO. The dendritic phthalocyanines containing tris are slightly soluble in water. The new compounds were characterized by elemental analysis and UV–vis, IR, NMR spectra. The temperature dependence of the dc and ac conductivity of these compounds and the adsorption of CO₂ gas on thin film of the compounds were investigated by dc conductivity and impedance spectroscopy technique using an interdigital transducer structure on glass substrate. While exposure to CO₂ have no influence on the electrical conductivity (ac and dc) of compound 6a and 6c, the conductivity of the film of 6b strongly depend on the presence of the CO₂ gas. Completely reversible sensor signals were obtained for compound 6b. The impedance spectra were obtained at frequencies between 40 and 10⁵ Hz, and in a wide range of CO₂ concentrations (from 500 to 8000 ppm) at room temperature. The temperature dependence of dc conductivity show typical Arrehenius behaviour for all compounds. The ac conductivity of the films is represented by the form ω^s. The dependency of frequency exponent s on temperature suggests a correlated barrier hopping (CBH).     

Metal ion sensing functional mono and double-decker lanthanide phthalocyanines: Synthesis,characterization and electrical properties

We report, in this study, the preparation, physical characterization metal ion sensing properties of peripherally functionalized ionophore ligand, 4,5-bis(6-hydroxyhexylthio)-1,2-dicyanobenzene (1) and its mono 2,3,7,8,12,13,17,18-octakis(6-hydroxyhexylthio)phthalocyaninatometal (II) {M = Zn^II (2), Cu^II (3)} and double-decker lanthanide bis-phthalocyanines, {([4,5,4′,5′ 4″,5″,4?,5?]-tetrakis-(6-hydroxyhexylthio)phthalocyaninatolanthanium(III)}){M[Pc(S–C₆H₁₃OH)₄]₂} {M = Eu^III (4), Yb^III (5), and Lu^III (6)}. All benzenes on phthalocyanines are functionalized with hydroxyhexylsulfanyl moieties for potential use as soft metal ion binding, such as Ag⁺ and Pd²⁺. The temperature dependence of the dc and ac conduction properties of 4, 5 and 6 thin films have been investigated in the frequency range of 40–10⁵ Hz and temperature range 290–436 K. The dc results showed an activated conductivity dependence on temperature for all films. Obtained data reveal that ac conductivity obeys the relation σ_ac(ω) = Aω^s and exponent is found to decrease by increasing temperature. The data obtained results were compared with the prediction of the Quantum Mechanical Tunelling (QMT) and Correlated Barrier Hopping (CBH) models. The analysis showed that the CBH model is the dominant conduction mechanism for the electron transport in the films. The new synthesized compounds have been characterized by elemental analysis, FTIR, ¹H and ¹³C NMR, MS, UV–vis and EPR spectral data.     

Photo-induced magnetization in copper(II) octacyanomolybdate(IV)

The photomagnetic effect of the mixed-valence compound Cu₂^II[Mo^IV(CN)₈]·7.6H₂O (Cu^II; 3d⁹, S=1/2, Mo^IV; 4d², S=0) (1) was investigated. The UV–VIS spectra showed the intervalence transfer (IT) band between Mo^IV–CN–Cu^II and Mo^V–CN–Cu^I around 500 nm. When the paramagnetic compound 1 was irradiated by a filtered blue light (400–430 nm, 3 mW/cm²) of a Xe lamp at 5 K, the irradiated sample exhibited a spontaneous magnetization with a Curie temperature of 17 K. By annealing the irradiated sample above 200 K, the magnetic property of this sample returned to the initial state. This photo-induced magnetization is explained by the following mechanism. The excitation of the IT band causes the electron transfer from Mo^IV (S=0) to Cu^II (S=1/2), producing a mixed-valence isomer of Mo^V (S=1/2)–CN–Cu^I (S=0). However, half of the copper ions remain as Cu^II ions due to the stoichiometric limitation and hence the irradiated 1 is expressed as Cu^ICu^II[Mo^V(CN)₈]·7.6H₂O. The unpaired electrons on Mo^V (S=1/2) ions and those on Cu^II (S=1/2) ions in the irradiated compound interact ferromagnetically, giving rise to the spontaneous magnetization.     

Preparation,electrochemistry and optical properties of unsymmetrical phthalocyanines bearing morpholine and tert-butylphenoxy substituents

The synthesis of novel, unsymmetrical, octasubstituted metal-free and metallophthalocyanines (zinc, cobalt) bearing one chlorine, one morpholine moieties and six 4-tert-butylphenoxy substituents was achieved by a statistical condensation reaction of two corresponding phthalonitriles. The new compounds have been characterized by using elemental analyses, UV–vis, IR, ¹H NMR and mass spectroscopic data. Voltammetric and spectroelectrochemical studies are in harmony with the reported metallophthalocyanine complexes, which support the proposed structure of the complexes.     

Hafnium binary alloys from experiments and first principles

Despite the increasing importance of hafnium in numerous technological applications, experimental and computational data on its binary alloys is sparse. In particular, data is scant on those binary systems believed to be phase-separating. We performed a comprehensive study of hafnium binary systems with alkali metals, alkaline earths, transition metals and metals, using high-throughput first-principles calculations. These computations predict novel unsuspected compounds in six binary systems previously believed to be phase-separating. They also predict a few unreported compounds in additional systems and indicate that some reported compounds may actually be unstable at low temperatures. We report the results for the following systems: AgHf, AlHf, AuHf, BaHf, BeHf, BiHf, CaHf, CdHf, CoHf, CrHf, CuHf, FeHf, GaHf, HfHg, HfIn, HfIr, HfK, HfLa, HfLi, HfMg, HfMn, HfMo,HfNa, HfNb, HfNi, HfOs, HfPb, HfPd, HfPt, HfRe, HfRh, HfRu, HfSc, HfSn, HfSr, HfTa, HfTc, HfTi, HfTl, HfV, HfW, HfY, HfZn and HfZr ( = systems in which the ab initio method predicts that no compounds are stable).     

The photovoltaic performance of new ruthenium complexes in DSSCs based on nanorod ZnO electrode

Three new heteroleptic ruthenium complexes, [Ru(L1)(dcbpy)(NCS)₂] Ru^II(4,7-diphenyl-1,10-phenanthroline-disulfonic acid disodium salt)(4,4′-dicarboxy-2,2′-bipyridyl)-di(thiocyanate) [K28], [Ru^II(L1)₂(NCS)₂] Ru^IIbis(4,7-diphenyl-1,10-phenanthroline-disulfonic acid disodium salt)-di(thiocyanate) [K313], and [Ru(L2)(dcbpy)(NCS)₂] Ru^II(1,10-phenanthroline-5,6-dione)(4,4′-dicarboxy-2,2′-bipyridyl)-di(thiocyanate) [K27], have been synthesized as sensitizers for dye-sensitized solar cells (DSSCs) using ZnO nanorod electrode. The photovoltaic performances of the solar cells based on these sensitizer dyes are studied under AM 1.5 irradiation (100 mW/cm²). Their photophysical and electrochemical properties are also investigated. ZnO nanorod based dye sensitized solar cell sensitized with K28 ruthenium complex bearing bulky sulfoxy groups gives an overall conversion efficiency of 2.51, a short-circuit current of 7.19 mA/cm², and an open circuit voltage of 550 mV. K28 is firstly designed and synthesized in the literature to increase molar extinction coefficients and enhanced spectral response in the visible light by expanding the π-conjugation, and of course to reduce back electron transfer due to the bulky sulfoxy groups. The vertical excitation energies, corresponding excitation wavelengths and oscillator strengths, predominant orbitals involved in ten singlet–singlet transitions and their characters obtained from the single point TD-DFT calculations have been obtained for K28.     

Corrosion resistance of painted zinc alloy coated steels

Organic coating in combination with sacrificial metal coating is the most popular method of protecting steel strips against atmospheric corrosion. Experiences over the years have proven that such duplex coating systems are best suited for the coil industry for the long term corrosion protection of steel. The excellent corrosion resistance of such systems has been attributed to the synergy between the cathodic protection provided by the sacrificial coating of zinc alloys and the combined barrier resistance of the metal and organic coatings. Traditionally continuously hot dip zinc-coated steels are used for such applications. However, off late the quest for further extending the longevity of the coil coatings has led to the replacement of the zinc coating with a host of other hot dip zinc–aluminium alloy coatings such as Galvalume^®, Galfan^®, ZAM^®, SuperDyma^®, etc. Each of these metal coatings has its own unique metallurgical features in terms of flexibility, bonding, microstructure and electrochemical characteristics which may significantly influence the performance of the organic coatings applied over it. This paper looks into the various aspects of these features of the hot dip coatings on the corrosion performance of the pre-painted steel strips. For simplicity only polyester paint system, the work horse of the coil industry, is considered.     

Dielectric investigation of MM(PO4)2 double orthophosphates (M = Ca, Sr, Ba, Pb; M = Ti, Zr, Hf, Ge, Sn)

M^IIM^IV(PO₄)₂ (M^II = Ca, Sr, Ba, Pb; M^IV = Ti, Zr, Hf, Ge, Sn) ceramics were prepared by solid state reaction method and consolidated by spark plasma sintering in order to study their electrical properties. The dielectric study performed at room temperature was aimed to determine the basic electrical properties of these compounds. Maxwell-Wagner polarization contributions, which are active at low frequencies cause a strong extrinsic increase of both real and imaginary part of permittivity as well of the dc-conductivity for BaZr(PO₄)₂, BaTi(PO₄)₂, BaHf(PO₄)₂, and SrGe(PO₄)₂ double orthophosphates. Moderate real (ε^′r=20-150) and imaginary low-frequency permittivity (ε^′r=7-300) and typical Debye relaxation with relaxation time in the range of ms is typical for: PbHf(PO₄)₂, PbZn(PO₄)₂, and CaGe(PO₄)₂. At high-frequency (f = 10⁹ Hz), the ceramics have permittivities of 2.29÷8.02 and tangent loss of 0.003÷0.153. The compounds SrGe(PO₄)₂, BaGe(PO₄)₂, BaZr(PO₄)₂ and BaSn(PO₄)₂ have excellent high-frequency dielectric characteristics, with losses of 3÷6% and permittivity slightly above 2 and are possible candidate as microwave ceramics.     

Oxide coatings modified with transition and rare-earth metals on aluminum and their activity in CO oxidation

Oxide catalysts, which, in addition to Al₂O₃ + SiO₂, contain from one (Ni) to four oxides or compounds of transition metals (Ni, Cu, Mn, and Co) and oxides or compounds of rare-earth elements (Ce, La), are produced on D16 aluminum alloy by plasma electrolytic oxidation combined with impregnation and subsequent annealing. The composites formed begin to catalyze the CO oxidation in a temperature range of from 100 to 300°C. The catalysts used can be arranged in the following series of decreasing catalytic activity: Ni-Cu-Mn-Co-Ce > Ni-Cu-Mn-Co-Ce-La ≈ Ni-Cu-Mn-Co > Ni-Cu-Mn > Ni-Cu > Ni. Oxygen compounds of Cu⁺, Cu²⁺, Mn⁴⁺, Co³⁺, Ce³⁺, and Ce⁴⁺, which seem to determine the catalytic properties of the oxide systems studied, are found on the surface and in the subsurface layer with a total thickness of ～6 nm of the most active Ni-Cu-Mn-Co-Ce catalyst.